1. Technical Field
Embodiments of the invention relate to a cryogenic system for superconducting magnets.
2. Discussion of Related Art
Superconducting magnets conduct electricity without resistance as long as magnets are maintained at a suitably low temperature, which is referred to as “superconducting temperature” herein after. Accordingly, cryogenic systems are used to ensure that the superconducting magnets work below the superconducting temperature.
One conventional cryogenic system uses a cooling coldhead which is mounted to the superconducting magnet. Such mounting of the cooling coldhead to the superconducting magnet has several disadvantages including the detrimental effects of stray magnetic fields on the coldhead motor, vibration transmission from the coldhead to the superconducting magnet, and temperature gradients along the thermal connections between the coldhead and the superconducting magnet.
Another conventional cryogenic system uses a large volume of liquid cryogen in a cryogen bath to cool the superconducting magnet. The heat of the superconducting magnet is removed by boiling off the liquid cryogen to gaseous cryogen. In some magnets, the boil off cryogen gas vents to the atmosphere and periodic cryogenic service to refill the cryogen is required. Some magnet uses a refrigerator or a cryocooler to re-condense the boil-off cryogen gas back into liquid. However, when the refrigeration is turned off by loss of electric power or during system maintenance, or when the magnet is quenching and the stored electromagnetic energy of the magnet is dumped into heat, there is a large amount of boil-off cryogen gas that vents to the atmosphere and be lost. Cryogenic service and cryogen refilling are also needed once the refrigeration is turned back on.
It may be desirable to have a different cryogenic system that contains very small volume of cryogen in a completely closed system so that no cryogen would ever differs from those systems that are currently available with minimized gaseous cryogen vented out of the cryogenic system.